Reading Comprehension: Sources of Difficulty and Neurocognitive Correlates It is well established that successful reading comprehension requires skilled word reading and strong language proficiency, and that word reading deficits are mainly responsible for reading comprehension deficits in some disabled readers at all ages. Beyond the primary grades, however, an increasingly high proportion of poor readers are able to read words accurately yet comprehend very poorly. This suggests that other factors are the source of their difficulty, and other compelling research findings converge on that conclusion also. At present, there is some extant evidence for at least two strong candidates, either or both of which could seriously impede successful comprehension of text: (1) inefficient (non-automatized) decoding of printed words in isolation and/or text, and (2) deficiencies in one or more aspects of language proficiency (including vocabulary, syntactic, and inferential skills). Many important questions remain unanswered, however, because these hypothesized influences on reading comprehension deficits (RCD) have not been comprehensively studied, especially in the crucial upper-elementary and middle school years when difficulties in comprehending text have such serious consequences for academic achievement in many school subjects. The goal of this project is to address these gaps in knowledge and thereby to clarify the bases for reading comprehension difficulties in fourth through eighth grade students. The independent and overlapping contributions of word reading, fluency, language, and memory skills to comprehension will be investigated in a large sample of students in grades 4 through 8. In the proposed studies, functional neuroimaging (fMRI) will be used to examine group differences in cortical activation during different reading tasks and structural MRI (Diffusion Tensor Imaging) will be used to examine the white matter fiber pathways hypothesized to be involved in reading. The findings will increase our understanding how the process of comprehending text can be disrupted, about whether reading comprehension deficits arise for different reasons in different children, and about the neurobiological underpinnings of comprehension processes. The knowledge gained from this research will thus provide more solid guidelines to researchers and educators regarding what types of reading disabilities occur in this period, what kinds of assessments are most appropriate for differentiating them, and what sorts of reading instruction are likely to be of greatest benefit.